The present invention relates to filtration generally and is more particularly directed to the removal of particulate material from water or the separation of oil and water, and is even more particularly directed to a rigid filter plate or support plate which may be utilized in gravity sludge dewatering or oil and water separation.
It is frequently necessary to remove suspended or dissolved particulate matter from water. This is frequently characterized as a sludge treatment process, or sludge dewatering. Sludge dewatering is commonly employed in water treatment plants or similar industrial applications. Similar filtration may be used in waste water or raw water treatment to remove or separate oil from water.
In the most common applications, water is caused to be flowed over or through the filter material by gravity means. As water flows through the material, by contact with the filter means, sludge or particulate or other solids are removed from the water. Oil may be removed from the water by similar means.
Unless the filter material can be cleaned, it is necessary to dispose of the filter material once sludge or other materials have built up on or within the filter. It is not economically feasible in most settings, such as in waste water treatment plants, to constantly dispose of filters. Accordingly, there must be a reasonable means by which to clean these filters.
One method of cleaning filters is by back wash, or by flowing water in a backwards fashion through the filter so as to wash out the accumulated sludge or other materials. This is a time consuming means of cleaning the filters and may cause a loss of filter material, or breakage of the filter.
A preferred way of cleaning the filters is by a mechanical means of scraping the accumulated sludge or other material off of the filters. However, this means is abusive to teh filters, especially when it contemplated that heavy equipment such as small bulldozers or front end loaders may be accomplishing this mechanical cleaning. Therefore, a very durable filter is required for this type of cleaning to be employed.
It has long been recognized that sand is a very effective filtration material for sludge dewatering. However, in the prior art, sand has been employed by loosely placing it on top of or within some supporting or containing structure. Sand cannot be cleaned by the mechanical means described above, since such mechanical cleaning would take the sand with it.
The prior art reveals rigid filter plates using aggregate type materials which are bonded together, and which will allow mechanical cleaning to be accomplished due to their durable nature. However, the materials are bonded such that it is frequently necessary to employ vacuum means to achieve the desired water flow through the filter plate. Especially after sludge or other material which is removed from the water has built up on the plate, gravity will not achieve a satisfactory rate of flow through the filter plate due to the restrictions created by the filter materials and the sludge.